LARSA: Bridge Geometry Control

LARSA 4D has advanced tools for modeling segmental and curved bridges, reducing the user's dependence on unintegrated, specialized applications for defining geometry.

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Bridge Path Coordinate Systems | Segmental Construction Methods

Bridge Path Coordinate Systems

The bridge path user coordinate system is a tool of convenience for modeling. Bridge paths are particularly useful in the setup of model geometry because they allow the user to work in very simple coordinates despite any curvature of the structure. This is accomplished by warping the usual x-axis into a curve that follows the twists and turns of the bridge.

In bridge paths, the warped x-axis is called the station axis. The curvature of the station axis is given by defining the path in two planes. Gometry control points at stations along the bridge define the path in the plan view. Circular and spiral curve fitting can be applied between control points to establish the curve of the path.

The elevation or vertical path is defined by a series of elevation points at stations along the path, with the elevation and grade at each point.

A LARSA project can have any number of bridge path coordinate systems. Different coordinate systems can be used to define bridge girders, spiral on- and off-ramps, and ground-level footings.

Stations, headings, and curve fitting options define the horizontal path of the bridge.

Vertical elevation geometry is defined by elevation control points and the grade at each point.

Segmental Construction Methods

The segmental contructruction options of LARSA 4D's Staged Construction Analysis make modeling balanced cantilever bridges easier than ever before. The hinged cast, matched cast, hoist, and dsplacement initialization options automatically adjust bridge geometry as new segments are cast to match the displacements of previous segments. These options make it possible to model bridges without knowing ahead of time how the bridge will deform.

The hinged cast option adjusts the casting location of new segments to match the vertical deformation of the previously cast segment. The matched cast option adjusts the casting location of the new segments so that they remain at the same angle with the previous segment.